The present invention relates to the treatment of a dry animal meal to produce products consisting of small peptides. These peptides are highly suitable for inclusion in animal feeds or edible food products. These peptides result from combining a method of alkaline liquification and proteolytic enzyme treatment.
Keil, et al., U.S. Pat. Nos. 2,431,256 and 2,477,255 describe a protein hydrolysis under severe conditions of alkalinity and temperature which result in a degradation of the amino acid quality of the end products. Sato, et al., U.S. Pat. No. 3,891,770, describes a waste water treatment procedure in which protein and fat are concentrated with the assistance of polyacrylate precipitating agent to prepare a froth. The patent to Bosund, et al., U.S. Pat. No. 3,924,005, describes a totally enzymatic process for solubilizing fish proteins.
In U.S. Pat. No. 4,473,589, by the present inventors, an improved process is described in which sources of protein, such as by-product residues from processing fish, poultry, pork and beef, are hydrolyzed to produce liquid products. In this process, the starting materials were the raw waste products which were heated in an aqueous slurry at an initial pH of at least 12 and at an elevated temperature of about 120.degree.-170.degree. F. for a time sufficient to rupture the cells and to liquefy the proteins. This treatment provides the means to pasteurize or sterilize the product, which markedly improves product quality. This involves the judicious use of both time, and temperature for the alkaline step with a pH of at least 12. The proteins were treated by enzymatic digestion at a temperature of about 100.degree.-140.degree. F. at an alkaline pH in the presence of an effective amount of a proteolytic enzyme. The end liquid product was a liquid containing both peptones and smaller polypeptides.
The process of U.S. Pat. No. 4,473,589 produces a good feed supplement or fertilizer. However, it relies on a source of fresh or raw undenatured protein material (e.g. offal) which is not always available throughout the year. Also, such sources are subject to wide variations in composition leading to difficulties in controlling the uniformity of the end product. Also, the raw materials tend to spoil quickly, generally requiring the liquefication processing plant to be near the raw material source. Also, the process is not optimally effective for offal of all animals. Further, fat in the offal remains in the final product which is undesirable for many potential end uses.
Thus, there is a need for a new improved process to convert animal byproducts into useful end products.